Optimized X-ray tube cooling device

ABSTRACT

A cooling system to cool the x-ray tube of a CT imaging system. The heat exchanger has a curved sector shape which provides a larger surface area for heat dissipation within the cover of the gantry. The axis of the cooling fans is preferably parallel to the rotational axis of the gantry.

CROSS-REFERENCE TO RELATED APPLICATIONS

This case is related to the subject matter as set forth in ProvisionalPatent Application Ser. No. ______ filed on May 22, 2003.

TECHNICAL FIELD

The present invention relates generally to CT imaging systems, and moreparticularly to imaging systems that use fans and heat exchangers aspart of the cooling systems.

BACKGROUND OF THE INVENTION

Computed tomography (CT) imaging systems are in wide use today. The CTsystems include a gantry that has a frame which rotates in order tocreate a 360° image. The gantry frame includes an x-ray tube as well asa cooling system to control the temperature of the x-ray tube. Thecooling system typically employs a liquid-to-air heat exchanger toremove heat from the x-ray tube during operation. The cooling systemalso typically includes one or more fans that are used to draw airthrough the heat exchanger and exhaust heated air from the gantry.

The size and surface area of the heat exchanger required in a particularapplication is partly a function of the power to be dissipated, and thetemperature of the ambient air sent through the heat exchanger. On highpower CT systems, the ambient air temperature in combination with thehigher power requirements often makes the packaging difficult for largeheat exchangers.

Also, when larger heat exchangers have been utilized, the axis ofrotation of the fans have not been parallel to the axis of rotation ofthe gantry, which leads to geoscopic loading. The fans are more reliablewhen their rotation axis is parallel to the gantry axis.

It would, therefore, be desirable to provide a heat exchanger with alarger surface area for cooling and still be confined in the spacerequirements of the gantry. It also would be desirable to have a largerarea heat exchanger and maintain the fan axis of rotation parallel tothe gantry axis of rotation.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved heatexchanger for the cooling system of a CT imaging system. It is anotherobject of the present invention to provide a package for a heatexchanger that presents a larger surface area to dissipate heat andstill maintain an axial air flow direction.

It is a still additional object of the present invention to provide acooling system for a CT imaging system that improves the thermalperformance of the CT system. It is still another object of the presentinvention to provide a cooling system that allows for greater heattransfer surface area of the heat exchanger and still allow the heatexchanger to be easily packaged in the gantry.

These and other objects of the present invention are accomplished by themethod apparatus and system set forth in the accompanying specification,drawings, and claims. In addition, the present invention has manybenefits and advantages over known apparatus, methods and systems whichare used to cool x-ray tubes in CT imaging systems.

In accordance with the present invention, the heat exchanger for thecooling system is shaped and provided to fit within as much of theallowable space as possible in the gantry. In this regard, gantrystypically have a tight fitting cover structure that generally has anannulus or “doughnut” shape. The inventive heat exchanger is preferablyshaped as a sector of an annulus with the curvature matching therotating envelope of the CT gantry. This shape presents the largestsurface area possible within the gantry to dissipate heat.

The heat exchanger is also positioned to allow air flow through it in adirection parallel to the axis of the gantry. This allows positioning ofthe cooling fans such that their axes of rotation is also parallel tothe gantry axis. This eliminates gyroscopic loading on the fan shaftwhen the fan axis and gantry axis are not in parallel.

Other aspects and advantages of the present invention will becomeapparent upon the following detailed description and appended claims,and upon reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, reference can bemade to the embodiments illustrated in greater detail in theaccompanying drawings and described below by way of examples:

FIG. 1 is a schematic illustration of a CT system illustrating itsgeneral components.

FIG. 2 illustrates a portion of the gantry system depicting several ofits internal components in accordance with the present invention.

FIG. 3 illustrates an embodiment of the present invention.

FIGS. 4, 5, and 6 are various views of a preferred heat exchanger inaccordance with an embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating the use of a deflector memberwith a heat exchanger; and

FIG. 8 is a schematic diagram illustrating an embodiment of theinventive heat exchanger with a deflector member.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In each of the following figures, the same reference numerals are usedto refer to the same components. Also, while the present inventions aredescribed with respect to apparatuses, systems, and methods of improvingcooling systems of computed tomography (CT) imaging systems, the presentinventions are capable of being adapted for various purposes are notlimited strictly to CT systems. For example, the present inventions canbe utilized in MRI systems, radio therapy systems, other x-ray imagingsystems, ultrasound systems, nuclear imaging systems, magnetic resonantspectroscopy systems, and other applications and systems known in theart.

Also, although the present invention is described as being used inconnection with x-ray tubes for CT imaging systems, the presentinvention can be used in conjunction with other imaging tubes, includingvascular tubes.

In the following description, various operating parameters andcomponents are described for preferred embodiments of the presentinvention. The specific parameters and embodiments are included only asexamples and are not meant to be limiting.

Referring now to FIG. 1, a schematic illustration of a conventionalcomputed tomography (CT) system is disclosed and referred to generallyby the reference numeral 10. The imaging system 10 includes a gantry 12that has an x-ray imaging tube 16. The imaging tube 16 projects a beamof x-rays toward a detector array 18.

When the CT imaging system is utilized, a patient 20 positioned on amovable slider tray mechanism 22 is positioned in the central bore 23.X-rays from the imaging tube 16 pass through the patient within the bore23 and are detected by the detector array 18 and used to create a CTimage or a construction.

FIG. 2 illustrates a number of the inner components of the gantry member12. The gantry has an outer cover or structure 13 and a rotating innerannular frame member 30 which rotates about a gantry axis 32. The framemember 30 has a number of components attached to it and which rotatewith it. These components include an x-ray tube 40, a heat exchanger 42,one or more fan members 50, two of which are shown in FIG. 2, and a fanmounting bracket 54. The cover 13 has at least one surface which ispositioned relatively close to the cooling system components as they arerotated inside the cover. Typically, the clearance is about 0.50 inchesto about 6.0 inches.

The CT system illustrated is simplified to highlight the aspects of thepresent invention. Those skilled in the art will recognize various othercomponents that need to be present and included in such systems. Forexample, CT system 10 also includes a controller which is preferablymicro-processor based. The controller is designed to control theoperation of the cooling system for the x-ray tube 40.

The cooling system includes as its principal components, the heatexchanger 42 and the fans 50. In this regard, the heat exchanger 42 ispreferably an oil-to-air heat exchanger and is also commonly called a“oil cooler.” Liquid-to-air types of heat exchangers are typically usedin x-ray systems. Also, in the embodiment shown in the drawings, thefans 50 are integrally coupled to the heat exchanger 42. Persons skilledin the art will recognize that one or more fans may be separatecomponents placed adjacent to the heat exchanger.

The cooling fans 50 are designed to help move air through the heatexchanger to cool the liquid circulating in the heat exchanger andultimately the x-ray tube 40. The controller (not shown) is operablycoupled to the fans to control their speed and thus control the amountof cooling in the system. In this regard, the speed of the fanpreferably varies over the operating temperature range of the x-raytube. When a predetermined temperature is reached, such as 100° F., thefan speed is elevated to maintain a maximum fan speed. The maximum fanspeed could be, for example, 2900 rpm. Also, the output of thecontroller and thus the operation of the fan does not necessarily haveto be linear.

An air deflector 60 is also shown in FIG. 2. An air deflector (a/k/a“visor”) is attached to the heat exchanger 42 and extends over the frontface 42A thereof. In this regard, air passing through the heat exchangeris introduced into the exchanger through front surface 42A and thus ispulled through the heat exchanger by the fans 50.

Another embodiment of the present invention is shown in FIG. 3. Asshown, the fan axis 64 is parallel to the gantry axis 32. This is thepreferred orientation of the air flow and fan rotation in accordancewith the present invention. In this manner, the fans 50 which areassociated with the heat exchanger 42, are oriented with the rotationalaxis parallel to their rotational axis of the gantry. This eliminatesgyroscopic loading on the fan shaft when the fan axis and gantry axisare not in parallel.

The cooling system is generally referred to by reference numeral 38 inFIG. 3 and also includes a pump 66 and a shroud member 70. The pump 66is used to circulate cooling oil through conduit 68 into and out of theheat exchanger 42. The shroud 70 is used to direct air passing throughthe heat exchanger through the fans 50.

The preferred shape of the heat exchanger 42 in accordance with thepresent invention is shown in FIGS. 4, 5, and 6. The heat exchanger isformed in the shape of a sector of an annulus and has a curvature 44that matches the rotating envelope of the CT gantry. The curved shape ofthe heat exchanger presents the largest surface area which can beutilized to dissipate heat from the gantry and CT imaging system withinthe gantry cover. There is a limited amount of space available in thetight fitting cover of the rotating gantry in conventional CT imagingsystems. Conventional heat exchangers are typically rectangular in shapeand are limited in size in order to allow the heat exchanger to fitwithin the available space.

It is also important with the present invention to position the heatexchanger in the manner and position shown in FIG. 2, i.e. with thesubstantially planar side surfaces 42A and 42B positioned to allow thefan to rotate about axes parallel to the gantry axis 32. The maintenanceof axial air flow through the heat exchanger and through the gantry ispreferred.

In the heat exchanger shown in FIGS. 4-6, the device has supportingand/or mounting members on the four perimeter surfaces. For example,curved brackets 45 and 46 are positioned on the upper and lowerperimeter surfaces, respectively, of the heat exchanger 42, whilemounting brackets 47 and 48 are positioned on the two end perimetersurfaces. The end mounting brackets 47 and 48 also contain varioushardware for inflow and outflow of the oil through the coils inside theheat exchanger (not shown). This hardware is referred to generally bythe reference numerals 49A-49F.

FIG. 7 schematically illustrates an air deflector 60 which can beutilized with the present invention in order to affect the air flowinside the gantry and prevent recirculation of heated air. As indicated,the air deflector or visor 60 is attached or connected to the heatexchanger 42. Cooler inlet air represented by arrow 90 is pulled intoand through the heat exchanger 42 by the fan 50, which is positionedimmediately behind the heat exchanger. Most of the air which passesthrough the fan 50 and the gantry 12 is exhausted through air vent 92,as represented by arrow 94.

However, as shown in FIG. 7, a portion of the heated air is oftenrecirculated inside the cover 13 of the gantry in a direction toward thefront surface 42A of the heat exchanger 42. This recirculated air isindicated by arrows 96. Without the air deflector 60 in place, therecirculated air, which is at an elevated temperature, follows the pathof the arrow 98 which is shown in dotted lines and passes back throughthe heat exchanger and fan.

Cooling air drawn into the heat exchanger is normally supplied by airthat is already present in the gantry during operation. The cooling airtemperature increases as it absorbs heat from the tube oil flowingthrough the heat exchanger 42. The heated air is preferably exhaustedfrom the heat exchanger through air vent 92. When the gantry is broughtto a stationary position, the heated exit air is directed to the airvents 92 on the gantry cover or structure 13. However, due to the closespacing between the gantry cover and the rotating cooling systemcomponents, some of the heated air is retained within the cover 13 andis reingested into the heat exchanger. When this happens, the x-ray tubeoil can stabilize at an elevated temperature and reduce the thermalperformance of the system. The use of an air deflector 60 reduces theingestion of previously heated air and forces the air going into theheat exchanger to come from the inboard regions of the gantry. The x-raytube oil thus runs at a lower nominal temperature resulting in increasedthermal performance of the CT system.

FIG. 8 is another schematic view of a gantry and cooling system inaccordance with the present invention. As illustrated, cool inlet air 90is drawn up through the gantry 12 through air vents 100 positioned inthe lower portions of the cover structure 13. The cooled inlet air isthen directed toward the front surface of the heat exchanger 42 asschematically shown in FIG. 7. The heat exchanger 42 has a curved(sector) shape and is positioned with the pair of fans 50 in order toallow air flow in an axial direction relative to the gantry axis ofrotation. An air deflector 60 can be added to prevent recirculation ofheated air.

While particular embodiments of the invention have been shown anddescribed, numerous variations and alternative embodiments will occur tothose skilled in the arm. Accordingly, it is intended that the inventionbe limited only in terms of the appended claims.

1-31. (canceled)
 32. A heat exchanger for containing a first coolantfrom a second coolant for cooling an x-ray tube having an axialdirection, said heat exchanger having a deflector wherein said deflectorextends axially from said heat exchanger, whereby said second coolant isaxially detoured by said deflector.
 33. The heat exchanger as describedin claim 32 wherein said heat exchanger has an upper perimeter surfaceand said deflector extends from said upper perimeter surface.
 34. Theheat exchanger as described in claim 32 wherein said heat exchanger hasan upper perimeter surface, a lower perimeter surface, a first endperimeter surface and a second end perimeter surface, said upperperimeter surface having a curved configuration, whereby said secondcoolant is bounded by said perimeter surfaces.
 35. The heat exchanger asdescribed in claim 34 wherein both of said upper perimeter surface andsaid lower perimeter surface have curved configurations.
 36. The heatexchanger as described in claim 34 wherein said curved configuration hasa constant radius of curvature.
 37. The heat exchanger as described inclaim 32 further comprising at least one fan member in operativeassociation with said heat exchanger, said fan member having an axis ofrotation substantially normal to said axial direction.
 38. The heatexchanger as described in claim 37 wherein two of said fan members areprovided, each of said fan members having an axis of rotationsubstantially normal to said axial direction of said heat exchanger. 39.The heat exchanger as described in claim 34 wherein at least one of saidfirst and second end perimeter surfaces has a mounting bracket thereon,and wherein at least one of said first and second end perimeter surfaceshas at least one liquid fixture thereon.
 40. The heat exchanger asdescribed in claim 39 wherein each of said first and second endperimeter surfaces has a mounting bracket thereon and wherein each ofsaid first and second end perimeter surfaces has at least one liquidfixture thereon.
 41. The heat exchanger as described in claim 32 whereinsaid heat exchanger has a shape substantially as a sector of an annulus,wherein said heat exchanger is configured for said second coolant toaxially pass through said sector of an annulus restrained by saiddeflector.
 42. A computed tomography (CT) imaging system comprising agantry member, said gantry member having a rotating frame member; anx-ray tube positioned on said frame member: a heat exchanger positionedon said frame member adjacent said x-ray tube and adapted to cool saidx-ray tube; at least one fan member positioned adjacent said heatexchanger and adapted to flow air through said heat exchanger; and adeflector wherein said deflector extends axially from said heatexchanger, wherein said heat exchanger is configured for air to axiallypass through said heat exchanged axially constrained by said deflector.43. The computer tomography (CT) imaging system as described in claim 42further comprising a shroud positioned between said heat exchanger andsaid at least one fan member.
 44. The computer tomography (CT) imagingsystem as described in claim 42 wherein said gantry member has a firstaxis of rotation and said fan member has a second axis of rotation, saidfirst and second axes of rotation being substantially parallel to oneanother.
 45. The computer tomography (CT) imaging system as described inclaim 42 wherein said heat exchanger having a configuration which issubstantially a section of an annulus, wherein said heat exchanger isconfigured for air to axially pass through said sector of an annulus,thereby increasing heat transfer to the air and decreasing substantiallythe recirculated air.
 46. The computer tomography (CT) imaging system asdescribed in claim 42 wherein said heat exchanger has an upper perimetersurface, a lower perimeter surface, a first end perimeter surface and asecond end perimeter surface, said deflector axially extending from saidupper perimeter surface and having a curved configuration, wherein theflow of air is bounded by said perimeter surfaces.
 47. The computertomography (CT) imaging system as described in claim 46 wherein both ofsaid upper perimeter surface and said lower perimeter surface havecurved configurations.
 48. The computer tomography (CT) imaging systemas described in claim 46 wherein said curved configuration has aconstant radius of curvature.
 49. The computer tomography (CT) imagingsystem as described in claim 42 wherein said heat exchanger is aliquid-to-air type heat exchanger, wherein said liquid is an oilmaterial.
 50. The computer tomography (CT) imaging system as describedin claim 46 wherein said deflector has a curvature that matches saidcurved configuration of said upper perimeter surface.
 51. The computertomography (Ca) imaging system as described in claim 42 furthercomprising a cover member covering said rotating frame member, x-raytube and heat exchanger, said cover member having at least one surfacewhich is spaced a distance of 0.50 to 6.0 inches from said heatexchanger.
 52. A computed tomography (Ca) imaging system comprising: agantry member, said gantry member having a rotating frame member; anx-ray tube positioned on said frame member; a heat exchanger positionedon said frame member adjacent said x-ray tube and adapted to cool saidx-ray tube; at least one fan member positioned adjacent said heatexchanger and adapted to flow air through said heat exchanger; a shroudpositioned between said heat exchanger and said at least one fan member;a deflector wherein said deflector extends axially from said heatexchanger, wherein said heat exchanger is configured for air to axiallypass through said heat exchanged axially constrained by said deflector;and a cover member covering said rotating frame member, x-ray tube andheat exchanger, said cover member having at least one surface which isspaced a distance of less than 6.0 inches from said heat exchanger,Wherein said gantry member has a first axis of rotation and said fanmember has a second axis of rotation, said first and second axes ofrotation being substantially parallel to one another, wherein said heatexchanger having a configuration which is substantially a section of anannulus, wherein said heat exchanger is configured for air to axiallypass through said sector of an annulus, wherein said heat exchanger hasan upper perimeter surface, a lower perimeter surface, a first endperimeter surface and a second end perimeter surface, said deflectoraxially extending from said upper perimeter surface and having a curvedconfiguration, wherein the flow of air is bounded by said perimetersurfaces and said deflector decreases the recirculated air.